4 ms·

So why would rocks do this but not the soil that’s already on the ground there? Isn’t it basically the same stuff?

barry-cotter 4y ago
The surface area of a mountain and the surface area of that mountain ground into fine gravel are very different. The same thing happens to the surface area in both cases, yes.
LarsAlereon 4y ago
The rock that's in the soil may not be the correct type, or it may have already reacted, or it may be in chunks that are too large to dissolve on human-relevant timescales. The idea is that you want ultramafic rocks, which are low in non-reactive Silica but rich in Magnesium and Iron oxides. These oxides absorb CO2 from the atmosphere to form carbonates and bicarbonates, sequestering it for geologic time. However, since reactions can only occur on the surface and when the minerals are dissolved, a big pile of mine spoil or river-sized rocks buried in the ground aren't doing much to absorb CO2. But if we grind it up into rock powder and spread it over fields, or crush it up into sand and dump it on beaches to let the ocean do much of the work of grinding and distributing it, the vastly increased surface area means a significant amount of CO2 can be absorbed in a human lifetime. There can also be pros or cons associated with the minerals in the rocks. For example, you don't want to spread rock containing heavy metals on fields where you grow food. On the other hand, rocks rich in Potassium are a beneficial fertilizer, and Iron-bearing rock spread in the ocean can encourage the growth of phytoplankton that further absorb CO2.
opportune 4y ago
Soil with CO2-absorbing minerals that’s already exposed to the air would already have absorbed the CO2. It’s like saying why plant trees to remove carbon from the atmosphere when we already have trees.
pfdietz 4y ago
Olivine is a particularly easily weather silicate, because the silicon atoms are in isolated SiO4(-4) tetrahedra. In most other silicates, the silica tetraheda are linked covalently by shared oxygen atoms and weather much more slowly.
baking 4y ago
The minerals in the soil have already been weathered and absorbed as much CO2 as they can. The important thing to understand is that it is only accelerating a natural process that has kept earth's temperature relatively stable for billions of years. This is true long-term carbon capture and it is worth researching the best way to do it.

The surface area of a mountain and the surface area of that mountain ground into fine gravel are very different. The same thing happens to the surface area in both cases, yes.

LarsAlereon 4y ago

The rock that's in the soil may not be the correct type, or it may have already reacted, or it may be in chunks that are too large to dissolve on human-relevant timescales. The idea is that you want ultramafic rocks, which are low in non-reactive Silica but rich in Magnesium and Iron oxides. These oxides absorb CO2 from the atmosphere to form carbonates and bicarbonates, sequestering it for geologic time. However, since reactions can only occur on the surface and when the minerals are dissolved, a big pile of mine spoil or river-sized rocks buried in the ground aren't doing much to absorb CO2. But if we grind it up into rock powder and spread it over fields, or crush it up into sand and dump it on beaches to let the ocean do much of the work of grinding and distributing it, the vastly increased surface area means a significant amount of CO2 can be absorbed in a human lifetime. There can also be pros or cons associated with the minerals in the rocks. For example, you don't want to spread rock containing heavy metals on fields where you grow food. On the other hand, rocks rich in Potassium are a beneficial fertilizer, and Iron-bearing rock spread in the ocean can encourage the growth of phytoplankton that further absorb CO2.

opportune 4y ago

Soil with CO2-absorbing minerals that’s already exposed to the air would already have absorbed the CO2. It’s like saying why plant trees to remove carbon from the atmosphere when we already have trees.

pfdietz 4y ago

Olivine is a particularly easily weather silicate, because the silicon atoms are in isolated SiO4(-4) tetrahedra. In most other silicates, the silica tetraheda are linked covalently by shared oxygen atoms and weather much more slowly.

baking 4y ago

The minerals in the soil have already been weathered and absorbed as much CO2 as they can. The important thing to understand is that it is only accelerating a natural process that has kept earth's temperature relatively stable for billions of years. This is true long-term carbon capture and it is worth researching the best way to do it.